Reproductive strategies of the red-tailed phascogale (Phascogale calura) Wendy Foster B.Sc. (Hons) Department of Ecology and Evolutionary Biology School of Earth and Environmental Sciences The University of Adelaide South Australia March 2008 A thesis submitted for the degree of Doctor of Philosophy at The University of Adelaide Who’s Your Daddy? Over the last year, there has been some action happening quietly behind the doors of the Animal Health and Research Centre, and I’m not referring to the treatment of sick animals. I’m talking about sex, and lots of it! This is Meanwhile, mum is left with eight babies to the six-hour continuous lovemaking that has raise without a single child support you hanging from the roof kind of sex. The payment. Luckily the young are born new partner every day kind of sex. The make smaller than a tic-tac, which makes giving love til you drop kind of sex. birth easier. Of the fourteen or so young born, only eight manage to find a teat – for What! I hear you exclaim. That’s outrageous! the others it is just bad luck. Mum carts the kids around continuously for about seven Well before you get too outraged maybe I weeks, then decides they are big enough to should clarify a couple of things. The stay in the nest while she goes ‘out on the individuals involved in this rampant love- tree’. Another seven weeks later and the making are an endangered carnivorous kids are finally ready to leave home, having marsupial known as the red-tailed phascogale. cleaned out mum’s pantry and strained her This species was once found over large regions sanity. Finally if she’s survived all that she of Australia, but is now only found in south- gets a bit of peace and quiet before jumping west WA, where they are rarely seen due to on the breeding roundabout again for a their small size and their tree-top antics second year. occurring at night. These sexy little creatures are the focus of As I alluded to above, their sex-life is not for my PhD project, which I’m doing with the the fainthearted. They only breed once a year assistance of Adelaide Zoo and Alice with mating occurring over a few weeks in Springs Desert Park. By learning more winter – maybe close body contact makes cold about their sex-life, we hope to be able to days easier to bear. Both males and females improve the management of phascogales in have multiple partners, which can result in a captivity with the plan to release them back litter of young having multiple fathers – so it into some of their former range. really is a question of ‘who’s your daddy?’ Though there are a lot of cute animals in the At the end of those several weeks of frenzied zoo, I happen to think the red-tailed sex, the males escape any parental duties by phascogales are the zoo’s sexiest animals. dying. Ah, the life of a male – live off mum What about you? for a quarter of your life, go out wandering the world for half your life while building up those muscles, then pick fights with any other bloke you meet, chase the girls and have sex as much as possible for the last quarter. In 'South Australia's Zoo Times'. pp. 14. Table of Contents Declaration ............................................................................................................................i Acknowledgements .............................................................................................................iii Conference presentations....................................................................................................v Additional manuscripts.......................................................................................................v Awards..................................................................................................................................v Abstract ............................................................................................................... 1 Introduction ........................................................................................................ 3 The paradox of sex...............................................................................................................3 Reproductive investment ....................................................................................................4 Limitations on female reproduction.................................................................................4 Limitations on male reproduction ....................................................................................5 Investment in offspring ....................................................................................................6 Polyandry .............................................................................................................................7 Sperm competition ...........................................................................................................8 Sperm choice....................................................................................................................8 Multiple paternity.............................................................................................................9 Male semelparous dasyurids – strategy I life history.....................................................10 Evolution of the strategy I life history .............................................................................11 Environmental predictability..........................................................................................11 Female mortality ............................................................................................................12 Sperm competition .........................................................................................................12 Reproductive investment in strategy I dasyurids ...........................................................12 Sex ratio .........................................................................................................................13 Size dimorphism ............................................................................................................13 Polyandry in strategy I species.........................................................................................14 Red-tailed phascogales ......................................................................................................15 Red-tailed phascogales as a model species ....................................................................16 Aims ....................................................................................................................................17 Timing of births and reproductive success in captive red-tailed phascogales, Phascogale calura....................................................................... 19 Statement of Authorship...................................................................................................20 Abstract ..............................................................................................................................21 Introduction .......................................................................................................................21 Methods ..............................................................................................................................23 Animals ..........................................................................................................................23 Body mass and pouch changes.......................................................................................23 Faecal hormones ............................................................................................................ 24 Sperm storage ................................................................................................................ 25 Estimate of sperm storage duration ............................................................................... 25 Timing of births and breeding success .......................................................................... 25 Results ................................................................................................................................ 26 Female body mass ......................................................................................................... 26 Pouch development of the female. ................................................................................ 26 Faecal hormones ............................................................................................................ 27 Sperm storage ................................................................................................................ 27 Estimate of sperm storage duration ............................................................................... 27 Timing of births............................................................................................................. 29 Breeding success............................................................................................................ 31 Discussion........................................................................................................................... 32 Acknowledgements............................................................................................................ 35 Changes in sperm production in a species exhibiting obligatory spermatogenic failure.......................................................................................37 Statement of Authorship .................................................................................................